1. Field of the Invention
This invention relates to electronic ignition systems for automobiles. More particularly, this invention relates to electronic ignition systems for vintage automobiles.
2. Description of the Related Art
FIGS. 1–3 depict an ignition system 10 originally installed in vintage automobiles such as, for example, the Ford Model-T, and commonly known as the “High Tension Jump Spark System”. As used herein, the term “vintage” is meant to include any automobile built between the years 1900 to 1930. The ignition system 10 includes the following main components: a commutator 12, induction coil assemblies 14, vibrating switches 16, spark plugs 18, high voltage wires 20, low voltage wires 22, and one or more power supply wires 24. Typically, the number of vibrating switches 16, induction coil assemblies 14, low voltage wires 22, and high voltage wires 20 is equal to the number of combustion cylinders in an associated internal combustion engine 26.
The commutator 12 is mounted to the internal combustion engine 26 and is electrically connected to primary windings in the induction coil assemblies 14 via the low voltage wires 22. As shown in FIG. 2, the commutator 12 includes a commutator cap 28 for receiving the four low-voltage wires 22. Each of the low-voltage wires 22 is electrically connected to a respective contact segment 30 in an internal rotary “raceway” 32 by threaded terminals 23. A roller contact 34 is mechanically coupled to, and rotates with, a cam shaft 36 of the engine 26. A fiber ring 33 electrically isolates the contact segments 30 from each other and from a steel outer housing 35 of the commutator cap 28.
As shown in FIG. 3, the induction coil assemblies 14 are mounted within a coil box 38, which is located within a passenger cabin of the automobile. Referring to FIGS. 1 and 3, the low voltage wires 22 are connected to terminals 40, which extend through a firewall of the vehicle and which are electrically connected to primary windings in each of the induction coil assemblies 14. The primary windings of each of the induction coil assemblies 14 are also electrically connected to a power supply device, such as a magneto, battery, or both, via terminals 42. A secondary winding within each of the induction coil assemblies 14 is electrically connected to a respective spark plug 18 via one high voltage wire 20. The spark plugs 18 are mounted within combustion cylinders in the internal combustion engine 26.
Mounted on the top of each of the coil assemblies 14 is a vibrating switch 16. Contact points of each vibrating switch 16 are electrically connected in a circuit containing the power source and the primary winding of the associated coil assembly 14.
In operation, the roller contact 34 is rotated by the cam shaft 36 of the engine 26, which causes the roller contact 34 to traverse around the raceway 32 and contact the contact segments 30 in an order corresponding to the firing sequence of the engine 26. The roller contact 34 remains in contact with each contact segment 30 for about 10 to 15 degrees of engine crankshaft rotation. When the roller contact 34 is in contact with the contact segment 30, the associated vibrating switch 16 is opened to collapse the magnetic field stored in the associated coil assembly 14, which induces electrical current in the secondary winding of the coil assembly 14. The electrical current induced in the secondary winding provides a voltage (about 8,000 to 20,000 volts) across a gap in an associated spark plug 18, which produces an arc for igniting fuel in the associated combustion cylinder.
While the ignition system 10 was successfully installed and operated in millions of vehicles, it was not without its faults. For example, the roller contact 34 within the commutator 12 and the contact points of the vibrating switches 16 are prone to wear. As these components become worn, engine operation becomes rough and inefficient, which can lead to premature failure of the engine.
The ignition system 10 is also known to provide some peculiar operating characteristics. For example, if a vehicle operator stops the engine with the roller contact 34 positioned on a contact segment 30 corresponding to a cylinder charged with fuel, the engine will re-start. In the Ford Model-T, for example, such re-starts are believed to occur as frequently as once every ten times the engine is stopped. Nonetheless, such re-starts are a surprise to the operator. Another peculiar operating feature of the ignition system 10 is the sound made by the vibrating switches 16, which, because the switches are mounted in the coil box 38 within the passenger cabin, can be heard by the vehicle's occupants.
Many advances in automotive ignition systems have been made in the years since the ignition system 10 was installed on new vehicles. The advance of electronic ignition systems has eliminated the need for many of the electrical contact points and moving parts found in the ignition system 10. As a result, modern electronic ignition systems provide for smoother running and more efficient engines that require much less maintenance.
Various kits are commercially available to replace the ignition system 10 with more advanced ignition systems. For example, a kit commercially available from Texas T Parts, 1820 Gray Stone Drive Bryan, Tex. provides a Kettering type ignition system for replacing the ignition system 10. In general, the Kettering type ignition system replaces the induction coil assemblies 14 with a single coil and replaces the vibrating switches 14 with a single master set of contact points connected to a condenser. A mechanical drive and housing associated with the contact points are mechanically coupled to the engine and, therefore, must be mounted in the engine compartment where they are plainly visible. As a result, such kits are not desirable to vintage automobile aficionados who wish to retain the automobile's original appearance.
Therefore, there remains a need for a replacement to the original ignition system in a vintage automobile that provides advances available in modern electronic ignition systems, while retaining the automobile's original appearance.